I have a Specialized Rockhopper from the 90's I'm converting to a single speed commuter. The cranks are those wide-armed, polished specialized cranks, and a big part of the reason I bought the frame was because I find them cranks to be so pretty.

Anyhoo, the middle ring has fine placement as far as chainline goes, but it's only like 34 teeth or something, so I want something bigger. The problem is, this crank's bcd is really small, it appears to be 74. All three chainrings (stamped steel) attach to the same point on the crank and the big and middle angle out from their bolt holes to create the gap between them. In other words they're not flat. So, I can't use the big chainring I have because the angle it sticks out puts it too far out or too far in if I put it on backwards.

My question is- where can I find a middle chainring replacement for this crank that's larger than the middle chainring that came with it? Or, where could I find a flat chainring larger than 34 with such a small bcd? I've searched the web and can't find anything.

Are the cheaper specialized cranks just not compatible with anything but their stock rings?